1. The field of art to which the invention pertains includes the art of tools and more specifically step-by-step operable machine wrenches.
2. Line valves having a threadedly connected bonnet and body construction are commonly utilized for high pressure, high temperature applications requiring extreme assembled tightness. Such tightness, which may for example require turning torques on the order of 3000 ft/lbs. to achieve, are readily attained during factory assembly but can represent a significant obstacle where in-line maintenance of the valve is to be subsequently conducted. Not only is the ability to disassemble and reassemble valves of this type without removing it from the line of paramount importance to the user, but because of the magnitude of torque indicated the use of large wrenches, impact wrenches, cheater bars or the like is generally precluded. Moreover, when such valves are used, for example, in the primary containment area of a nuclear power plant, the presence of borated water crystals restricts the use of pneumatic power devices or the like while the use of adjacent piping to provide reaction torque is frequently prohibited by governmental code. At the same time, such valves are usually manufactured without any provision for a wrench attachment while the machining of keyways, slots, flats or spanner holes in the valve bonnet is not permitted on site. Consequently, there has been a long-felt need for wrench apparatus capable of functioning for these purposes. Despite recognition of the problem and with knowledge of power wrenches such as disclosed, for example, in U.S. Pat. Nos. 4,027,560 and 4,027,561, a ready solution for this specific requirement has not heretofore been known.